• Nuclear Engineering and Technology
• /
• v.55 no.4
• /
• pp.1342-1349
• /
• 2023

The planning accuracy of charged particle therapy (CPT) is subject to the accuracy of stopping power (SP) estimation. In this study, we propose a method of deriving a pseudo-triple-energy CT (pTECT) that can be achievable in the existing dual-energy CT (DECT) systems for better SP estimation. In order to remove the direct effect of errors in CT values, relative CT values according to three scanning voltage settings were used. CT values of each tissue substitute phantom were measured to show the non-linearity of the values thereby suggesting the absolute difference and ratio of CT values as parameters for SP estimation. Electron density, effective atomic number (EAN), mean excitation energy and SP were calculated based on these parameters. Two of conventional methods were implemented and compared to the proposed pTECT method in terms of residuals, absolute error and root-mean-square-error (RMSE). The proposed method outperformed the comparison methods in every evaluation metrics. Especially, the estimation error for EAN and mean excitation using pTECT were converging to zero. In this proof-of-concept study, we showed the feasibility of using three CT values for accurate SP estimation. Our suggested pTECT method indicates potential clinical utility of spectral CT imaging for CPT planning.

• Nuclear Engineering and Technology
• /
• v.55 no.5
• /
• pp.1911-1923
• /
• 2023

The nuclear safety assessment involving large transient simulations is forcing the community to develop methods for coupling thermal-hydraulics and neutronic codes and three-dimensional (3D) Computational Fluid Dynamics (CFD) codes. In this paper a set of dynamic boundary conditions are implemented in OpenFOAM^Ⓡ in order to apply zero-dimensional (0D) approaches coupling with 3D thermal-hydraulic simulation in a single framework. This boundary conditions are applied to model pipelines, tanks, pumps, and heat exchangers. On a first stage, four tests are perform in order to assess the implementations. The results are compared with experimental data, full 3D CFD, and system code simulations, finding a general good agreement. The semi-implicit implementation nature of these boundary conditions has shown robustness and accuracy for large time steps. Finally, an application case, consisting of a simplified open pool with a cooling external circuit is solved to remark the capability of the tool to simulate thermal hydraulic systems commonly found in nuclear installations.

• Journal of ILASS-Korea
• /
• v.28 no.4
• /
• pp.176-183
• /
• 2023

Many countries are striving to reduce carbon emissions with the goal of net zero by 2050. Accordingly, vehicles are rapidly being electrified to reduce greenhouse gases in the transportation sector. However, many organizations predict that internal combustion engines of LDV (light-duty vehicle) will exist even in 2050, and it is difficult to electrify aircraft and large ships in a short time. Therefore, synthetic fuel (i.e., e-Fuel) that can reduce carbon emissions and replace existing fossil fuels is in the spotlight. The e-Fuel refers to a fuel synthesized by using carbon obtained through various carbon capture technologies and green hydrogen produced by eco-friendly renewable energy. The purpose of this study is to compare and analyze the injection and spray characteristics of the simulated e-Gasoline. We mixed the hydrocarbon fuel components according to the composition ratio of the synthetic fuel produced based on the FT(Fischer-Tropsch) process. As a result of injection rate measurement, simulated e-Gasoline showed no significant difference in injection delay and injection period compared to standard gasoline. However, due to the low vapor pressure of the simulated e-Gasoline, the spray tip penetration (STP) was lower, and the size of spray droplets was larger than that of traditional gasoline.

• Journal of Korea Society of Industrial Information Systems
• /
• v.28 no.6
• /
• pp.115-129
• /
• 2023

This study compares and analyzes domestic and international carbon prices through CPS, which represents the level of carbon pricing. The results show that countries implementing carbon taxes had lower carbon intensity compared to those that did not. The introduction of a carbon tax is expected to enhance energy efficiency and reduce carbon emissions. As the carbon price rises to the level required for carbon neutrality, CPS decreases significantly, particularly in the residential and commercial sectors. Therefore, it is necessary to introduce a carbon tax in the country to reach the required carbon price level for carbon neutrality, with a priority on introducing it in the residential and commercial sectors.

• Transactions of the Korean hydrogen and new energy society
• /
• v.35 no.2
• /
• pp.175-184
• /
• 2024

This study focuses on investigating the importance of managing greenhouse gas emissions from global energy consumption, specifically examining domestic targets for clean hydrogen production. Using life cycle assessment, we evaluated reductions in global warming potential and assessed the carbon neutrality contribution of the domestic hydrogen sector. Transitioning from brown or grey hydrogen to blue or green hydrogen can significantly reduce emissions, potentially lowering CO₂ equivalent levels by 2030 and 2050. These research findings underscore the effectiveness of clean hydrogen as an energy management strategy and offer valuable insights for technology development.

• Nuclear Engineering and Technology
• /
• v.56 no.4
• /
• pp.1398-1406
• /
• 2024

The control rod worth is a key safety parameter required to be measured in commercial pressurized water reactors (PWRs). Conventionally, the control rod worth is measured after reaching the critical state, which occupies the considerable time in the zero-power physics test. In this study, an efficient control-rod worth measurement technique has been proposed based on the improved neutron-source multiplication method, which can be implemented with the source-range detector count rates in the subcritical states. Moreover, the noise reduction technique has been adopted to smooth the large fluctuation existing in the original signals. In order to verify the engineering performance of the proposed measurement technique, the measured source-range detector count rates during the rod withdrawal process before reaching critical state in a CNP1000 reactor have been employed. It demonstrated that almost all estimated results of control rod worth satisfy the engineering acceptance criteria, except one control rod with the relative difference over 10 %, which indicates the capability of the proposed method in estimating control rod worth.

• Nuclear Engineering and Technology
• /
• v.56 no.4
• /
• pp.1296-1309
• /
• 2024

The aim of this work is to explore the effect of the double subdiffusion on the stability in BWRs. A BWR novel reduced order model with double subdiffusion effects: reduced order fractional model (DS-F-ROM) to describe the neutron and heat transfer processes was proposed for this study. The double subdiffusion was developed with a fractional-order two-equation model, and with different fractional-orders and relaxation times. The stability analysis was carried out using the root-locus method and change from the s to the W domain and were confirmed using the time-domain evolution of neutron flux for a unit step change in reactivity. The results obtained using the reduced fractional-order model are presented for different anomalous diffusion coefficient values. Results are compared with normal diffusion and P1 equations, which are obtained straightforwardly with DS-ROM when relaxation time tends to zero, and when the anomalous diffusion coefficient tends to one, respectively.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
• /
• v.46
• /
• pp.265-313
• /
• 2010

Kyoto Protocol is an international convention on concrete performance program for UNFCCC(United Nations Framework Convention on Climate Change), which regulate and prevent to global warming and officially came into effect on February 16, 2005. Kyoto flexible mechanisms, the agreed environmental system in March 1997 in the Third Conference of Parties in UNFCCC General Assembly, Emission Trading System(ETS), Clean Development Mechanism(CDM) and Joint Implementation(JI), are key policies related to environment. In advanced countries, greenhouse gas emissions should be reduced average 5.2% level compared to 1990 in total emissions during 2008-2012. World leading carbon market finished the trial on the EU ETS I greenhouse gas emissions trading system, EU ETS II is operated regularly after 2008. World Bank leads to make 'Prototype Carbon Fund(PCF)' in April 2004, which is the world first carbon fund and a representative public carbon fund type, World Bank operate various funds including present PCF. Thus, I would like to propose as follows in relation to this study: First, in the validity analysis of carbon funds, it would be needed to analyze the Emission Reduction Cost Efficiency(ERCE) of carbon. The ERCE is a break-even value which brings the Net Present Value(NPV) to zero. NPV approach is used among projects and it enables potential projects to be compared and evaluated the ERCE on the basis of the net present value of net future cash flows. Therefore, according to results of analysis, carbon funds should be developed and invested. Second, it would be necessary to allow of issuing bonds together with carbon funds, carbon finance etc. Third, carbon funds, it would be reasonable to have a relatively enough maturity in project and as a financial derivatives in the international financial markets, it is needed various types of transactions. Fourth, it would be needed to standardize the carbon emissions trading for more efficiently. Fifth, it would be necessary to establish and invest in various kinds of domestic and overseas global carbon funds, including governments, privates, governments and privates sectors. And it is also needed to establish the medium and long term plans for carbon funds. Sixth, it would be needed to foster the advanced trade mechanisms for carbon funds in the most effective ways. Finally, carbon funds should be used in harmony with international societies to reduce global warming as the social responsible investing funds and it should be contribute to sustainable development. In addition, it would seem that carbon funds should be studied on establishing the contributable standard of sustainable development in the future assignment.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.12 no.2
• /
• pp.328-335
• /
• 2008

The system performance of NRZ format in WDM transmission system with lumped dispersion management(DM) and optical phase conjugator(OPC) is compared with that of RZ format. It is confirmed that eye opening penalty(EOP) of both NRZ and RZ format in WDM transmission system having lumped DM combined with OPC are greatly improved than those in WDM system with only OPC. The optimal net residual dispersion(NRD) in the case of RZ format is decided to so small value that path-averaged dispersion coefficient become almost zero, while that in the case of NRZ format is decided to larger value, for the best improvement of overall WDM channels. It is also confirmed that EOP in the case of RZ format is more improved than that in the case of NRZ format in lumped DM with optimal NRD. This is resulted from that lumped DM combined with OPC suppress the signal distortion due to intrachannel four-wave mixing(IFWM) and intrachannel cross phase modulation(IXPM). Consequently, lumped DM combined with OPC proposed in this paper is effective technique to mitigate intrachannel nonlinearities in WDM transmitting RZ format.

• Korean journal of applied entomology
• /
• v.42 no.3
• /
• pp.211-216
• /
• 2003

Development and reproduction of Dichromothrips smithi were investigated under different temperatures, Durations of the development from egg to pre-adult of D. smithi were measured under 11 temperature ranges and it was 44.0 days at 13$^{\circ}C$ and 8.7 days at 32$^{\circ}C$. Developmental zero point and total effective temperature for the development of egg and larva, prepupa, pupa and for the complete development (egg to emergence) were 9.4, 8.9, 10.5, 10.8 and 9.5$^{\circ}C$, and 46.1, 90.1, 23.9, 41.2 and 204.4 degree days, respectively. The adult longevity was 28.3 days at 15 C and 14.3 days at 30$^{\circ}C$. The highest average fecundity per female was 69.3 at 25 C. The highest intrinsic rate of natural increase (r$\_$m/) and the highest net reproduction rate (R$\_$o/) were 0.241 at 30$^{\circ}C$ and 56.56 at 25$^{\circ}C$. The optimum temperature range for the growth of D. smithi was between 25$^{\circ}C$ and 30$^{\circ}C$.